Several unexpected behaviours

[jl5000]

I've been using S7 to create different types of parent and child classes and I'm seeing some unexpected results.

I create class_a below which works as expected, apart from the unhelpful error message when trying to set a read-only property.

When creating class_b I am expecting the property definition of the parent class to be overwritten, allowing x to be undefined (and therefore an empty chr vector). However it complains that it is NULL. when I try setting it to a non-empty value it still errors.

library(S7)

class_a <- new_class("class_a",
                     properties = list(
                       x = new_property(class_character,
                                        getter = function(self) "a",
                                        validator = function(value){
                                          if(length(value) == 0)
                                            "Error"
                                        })
                     ))

class_a()
#> <class_a>
#>  @ x: chr "a"
class_a("b")
#> Error in class_a("b"): unused argument ("b")

class_b <- new_class("class_b", parent = class_a,
                     properties = list(
                       x = class_character
                     )
)

class_b()
#> Error: <class_b> object properties are invalid:
#> - @x must be <character>, not <NULL>
class_b("b")
#> Error in class_b("b"): unused argument ("b")

^{Created on 2023-10-08 with reprex v2.0.2}

[hadley]

I don't think we can create a better error "unused argument" because class_a() is a regular function with one argument for each settable property.

The second problem is really #352; it shouldn't be possible to override properties in subclasses (at least in the way that properties are implemented in S7).